The invention relates to a reversing valve.
DE 40 25 115 A1 describes a damping valve having a damping valve body, elevated damping valve body regions being formed which emerge from a damping valve base body and which form valve bearing surfaces, having passage ducts which are covered by valve plates, at least one annular valve plate being arranged on the valve bearing surfaces and having at least one pre-opening cross section which is congruent with a passage duct, the pre-opening cross section being covered by a reversing plate which, when subjected to a flow from the passage duct, can lift off from the valve plate in the axial direction of the valve body. This theoretically good design of a direction-dependent pre-opening cross section has, however, the disadvantage that if the reversing plate is suddenly subjected to a flow a lifting-off movement is carried out which is so rapid that it brings the reversing plate to bear against the above arranged valve plate. The problem arises of how to counteract the sticking of the reversing plate at the valve plate without possible spring forces excessively influencing the opening characteristics of the reversing plate. The sticking effect cannot occur in the embodiment variant according to FIG. 1 of DE 40 25 115 A1, but the deformation forces which are necessary to allow the reversing plate to lift off are clearly discernible.
U.S. Pat. No. 5,261,448 describes a reversing valve having a valve body which separates two working spaces which are filled with a fluid. The valve body has passage openings which are covered at least partially by a number of valve plates. The passage cross section of the passage openings is controlled by a reversing plate as a function of the direction of flow. The reversing plate has spring sections which extend in the circumferential direction. The valve has at least one cover surface and clamping surfaces which the reversing plate prestresses outside the cover surfaces and the spring elements against the reversing valve. The at least one cover surface is aligned with at least one passage opening. The limited spring section is deformed in the transverse direction so that a small spring rate is obtained if the spring section is made as narrow as possible in the circumferential direction, which, however, conflicts with the need for rigidity.
The object of the present invention is to provide a reversing valve with a throttle passage which is effective as a function of direction, in such a way that the switching movement of the valve elements which clear the throttle cross section can proceed with minimum forces, while ensuring a secure closure to the other direction of pressure.
It is a further object to obtain reliable operating characteristics and the highest possible degree of fatigue strength.
According to the invention, the reliable operating characteristics are achieved in that the reversing plate has a recess which has a meandering shape in the vicinity of the cover surfaces.
The meandering configuration of the recess enables the cover surface to be made as small as possible. A small cover surface results in lower adhesive forces at the valve so that the dispersion of forces due to the adhesive forces is reduced.
In the invention, increased rigidity is obtained in that independently of, or in combination with the means of obtaining the reliable operating characteristics, two recesses are formed, one of which is concentric with respect to the center point of the reversing plate and is at least semi-helical over one longitudinal section, the inner recess being made in the surface region which is enclosed by the semi-helical longitudinal section of the recess, with the result that at least three concentric recesses extend over a circumferential section and bound the spring section.
This construction provides two advantages. Firstly, only three pitch circles are required for the recesses. A larger cross-sectional region is thus available for the inner and outer clamping surfaces. Furthermore, particularly long spring sections, which reduce the flow pressure necessary to lift off the cover surfaces, are obtained.
According to a further advantageous embodiment, the recesses are symmetrical with respect to at least one connecting web between the outer clamping surface and the inner clamping surface. Here, the connecting web is oriented diametrically with respect to the cover surfaces. The connecting web also provides an advantage in terms of rigidity, because the stresses which occur within the reversing plate when the cover surface lifts off are better absorbed.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.